This invention relates generally to prostheses for repairing diseased or damaged sections of a body passageway and more specifically to vascular grafts for repair of damaged or diseased sections of body vessels such as blood vessels.
Diseased or damaged blood vessels which may weaken, develop into aneurysms and rupture have conventionally been treated by invasive surgical techniques which surgically expose the section to be repaired. The section is resected and replaced either by a section of healthy vessel removed from some other site of the patient or by a tubular synthetic graft. The graft is sutured in place. Alternatively, it has been suggested in U.S. Pat. Nos. 3,657,744 and 5,078,726, that the graft be held in place by stents disposed inside the end portions of the graft and expanded to firmly affix the end portion walls of the graft between the expanded stent and the vessel walls.
Recently, it has been suggested to replace the invasive surgical techniques and the treatment of diseased or damaged iliac or aortic vessels with so-called minimally invasive or interventional procedures whereby a small incision in a femoral artery of the patient is made and the graft-stent combination is delivered to the desired site by way of catheterization. Once delivered, the graft is affixed in place by expanding the stent and, in order to do this without invasive surgery, such expansion is accomplished by use of one or more angioplasty-like balloon catheters with the inflation balloon or balloons employed to expand each of these stents. Such systems and suggestions are described in U.S. Pat. Nos. 4,577,631 and 5,078,726.
As described in the above-cited patents, the tubular graft is inserted into the vessel and is of a length sufficient to span the weakened sections of the blood vessel to be repaired and to overlap the healthy sections on either side of the weakened section. Once emplaced, the ends of the graft are affixed to the healthy sections by expanding a stent placed therein. The length of the weakened section will of course, vary from case to case. Because it is desirable to employ a length of graft which is sufficient to span the weakened section and only a minimal length of healthy sections necessary for good retention, reasonably close tolerances are necessary in properly choosing a length of graft to be employed. Ultimately, irrespective of the length provided by the manufacturer or selected by the doctor, fine adjustments must be made in a length in order to properly emplace the graft. Heretofore, these adjustments have been accomplished by virtue of the longitudinal elasticity, if any, present in the materials of construction from which the grafts are manufactured. Since such elasticity is relatively limited and, in some cases, nonexistent, the great burden of choosing the proper length of graft has been left to the skill of the doctor and frequently has presented the doctor with difficulties.
A similar problem exists at the ends of the graft wherein the ends of the graft are held in place by being sandwiched between the healthy portion of the blood vessel and an expanded stent. In order to do this, the end portions of the graft must be such that they can be affixed to the stent when the stent is unexpanded and then increased in diameter, together with the stent as the stent is expanded towards the walls of the blood vessel. Accordingly, the ends of the graft must also have elasticity, albeit radial elasticity. Again, while to a degree and some graft materials are inherently elastic in the radial direction, it is important to increase the degrees of freedom in choosing a proper graft size. Therefore, it is desirable for the manufacturer to provide the doctor with a wider range of elastic expansion than is assured by reliance on the inherent elasticity of the graft materials of construction.
Accordingly, there is a need for a graft which provides great freedom of both longitudinal and radial expansion at the central and end portions, respectively.